1. Star Spectra
Essential Question? How is information from what we see so informative about stars?

2. What does the light tell us?
When you look at a star, the light can
tell you a number of things.
▪ the distance of the star/lighted object
▪ What it’s made of relative to the elements

3. So what is light? Kurtzgesagt-Light
Light is energy produced by a photon
A photon is energy released as electrons move from different energy levels in an atom.
Visible light is only a very small part of the electromagnetic spectrum
Light has different frequencies but travels at the same speed (the speed of light) which is about 300,000,000 m/s

4. So what is light (cont)

6. So what is light? The Speed of light is approximately 300,000,000 m/s
That’s why you see the lightning before you hear the thunder

7. Luminosity Actual Brightness Or Visual Magnitude of the light.
Flashlight vs. Headlight of a car???

8. Luminosity vs. Apparent brightness
Actual Brightness Or “Absolute Magnitude of the light”.
It’s the total energy a star radiates per second.
Think: Flashlight vs. Headlight of a car???
Apparent Brightness
-what it “appears to be”
Also called visual magnitude
Depends on how far you are from the source.
Think: 2 flashlights- different distances

9. Luminosity vs Apparent Brightness
tells us a lot about the distance of objects.

10. What are spectra?
Spectra are the colors of light emitted when an electron (e’) jumps from energy level to energy level within an atom.
A light wave of a particular wave length is emitted.
All elements have their own unique spectra.
A spectra shown by a particular light tells us what it’s made of.

11. Absorption Line Spectra. Caused by a cold gas in front of a hot source
Blackbody spectrum- produced
by HOT solid/liquid or dense
Gas.
Bright line spectra-Produced by
thin hot gasses. Colorful
lines on black background.
Absorption Line Spectra.
Caused by a cold gas in front
of a hot source

12. Fraunhofer Lines in the spectrum of the Sun
The Solar Spectrum
Fraunhofer Lines in the spectrum of the Sun

13. Fraunhofer Lines in the Solar Spectrum (~1817)
Designation Wavelength Origin
A nm terrestrial oxygen
B terrestrial oxygen
C hydrogen (H alpha)
D neutral sodium (Na I)
E neutral iron (Fe I)
F hydrogen (H beta)
G metal blend
H ionized Calcium (Ca II)
K ionized Calcium (Ca II)

14. What does this tell us?
▪ the distance of Stars/lighted objects in the night sky
▪ the type of gasses the star is made of
▪ What it’s made of relative to the elements